Torque converters commonly employ thrust bearings between the impeller and stator and turbine and stator blades to carry the axial components of force produced between such torque producing blades of the converters.
Thrust bearings commonly employ a roller cage that is made either from stamped or formed steel or from solid bronze. The formed steel cage has the advantage of being much cheaper and much lighter than the bronze cage. The bronze cage, on the other hand, is stronger than the steel cage.
In very large torque converters used in large earthmoving vehicles, such as off-highway mining trucks and wheel loaders, manufacturing tolerances increase dramatically. As a consequence, it is difficult to prevent a significant amount of end play between the torque converter components. When the axial forces diverge from the thrust bearing, the end play can allow the thrust bearing rollers to become unloaded. As a consequence, the rollers are not maintained in sufficient contact with its relatively rotating races to maintain the speed of the thrust bearing with that of the races. This, in turn, allows the roller and cage to slow down or lag behind the speed of the races when the bearing rollers are unloaded. During operation, however, the axial forces can abruptly change directions, such as during downhill down shifts or when reversing vehicle directions under load. When this occurs, the thrust bearing becomes instantaneously loaded and must accelerate up to the speed of the races. As a consequence, acceleration forces are produced on the rollers, which in turn, are transmitted to the roller cage. Such acceleration forces are sufficiently high in the very large thrust bearings used in large torque converters due to their greater mass that it causes the premature failure of the steel bearing cages due to fatigue. On the other hand, if a stronger bronze bearing cage is used instead of a steel cage, the much greater mass of the bronze cage is sufficient to slow the acceleration of rollers and cage to cause roller skidding on the races. Such skidding produces flat spotting on the rollers and excessive wear on the races, also resulting in premature bearing failure, along with expensive down time of the vehicle and repair costs.
The present invention is directed toward eliminating the above-noted bearing failure problems.